Short-term test procedures are under development for the prediction of the long-term consequences of blood-material interactions (BMI) using well characterized materials. The predictive tests under development will be validated by long-term evaluaton studies. Polymethylmethacrylate and Avcothane-51(R), prepared at AERL, and low density polyethyleneand silica-free polydimethylsiloxane primary reference materials, supplied by NIH, will be tested in the form of flat sheets and 5 mm O.D. x 4 mm I.D. tubes. The preparation and characterization of all materials and methods have progressed to the point of actual material blood compatibility evaluation.